Java 2d: slow down rotation (like a wheel of fortune)

user_5733078 0
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I'm trying to create a wheel of fortune game.

Everything is working fine but I can't find a realistic way to decelerate the wheel rotation speed.

Currently I just tried to do something like this:

    if (spin > 3) spin-=0.030;
    if (spin > 2) spin-=0.020;
    if (spin > 1) spin-=0.015;
    if (spin > 0.5) spin-=0.010;
    if (spin > 0) spin-=0.005;
    if (spin < 0) spin=0;

But of course it's not a very nice approach, and even changing values here and there the result is not really satisfying.

What would be the mathematical function to gradually slow down the rotation?

rotation java
2 Answers

You might try the following:

final float DECEL = 0.95;
final float FRICTION = 0.001;
spin = spin * DECEL - FRICTION;

This assumes that this is getting called on a regular time interval. The extra "- FRICTION" is there, so that the wheel will actually stop.

If your drawing loop is getting called with a time delta since the last frame draw, then you would use that to adjust the DECEL and FRICTION parameters. For example, you might have:

final float DECEL = 0.95;
final float FRICTION = 0.001;
// calculate how much the wheel will slow down
float slowdown = spin - (spin * DECEL - friction);

// Apply the frametime delta to that
slowdown *= frameDelta;
spin = spin - slowdown;

This, of course, will take some experimentation with the DECEL and FRICTION parameters.

user_13850830

You could try to model the slowdown by using an exponentially decreasing equation that equals your spin speed. Then stop the spinning wheel by putting a limit on how long it spins (as y=0 is an asymptote in an exponential eq.). 

float spinSpeed;  //will track the spinning speed using an equation
double spinTime = 4;  //limits total spin time using an equation

for (i=1;i<=4;i++) {  //will track time in seconds
spinSpeed = math.pow[5.(-i+3)];  //equivalent  to y=5^(-(x-3))
}  //be sure to import math
user_102395170
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